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I I APPENDIX C MONITORING WELL INSTALLATION AND DEVELOPMENT PROCEDURES Following RWQCB acceptance of the proposed well locations, the monitoring wells will be installed in the uppermost groundwater zone to evaluate Site groundwater flow conditions and the concentrations and extent of toluene in groundwater at the Site. Four, two-inch diameter groundwater monitoring wells will be installed. As part of this task, Geosyntec will perform the following activities: • Mark well locations and arrange for permitting and underground utility clearance; • Update the project health and safety plan, as necessary; • Drill and install the monitoring wells; • Survey the wells; and • Develop and sample the wells. Well Location,Permitting,and Underground Utility Clearances Geosyntec will visit the Site to mark well locations for underground utility clearances and notify Underground Service Alert (USA) a minimum of two business days before drilling. Each well location will also be cleared by a private utility locator. Geosyntec will obtain well permits from the County prior to beginning field activities. Drilling and Installation of Groundwater Monitoring Wells Four, two-inch diameter monitoring wells (DMW-1, DMW-2, DMW-3, and DMW-4) will be installed in the uppermost groundwater, at the locations that will be proposed following the completion of Task 2. First groundwater was encountered between approximately 15 and 20 ft bgs during the past investigations at the Site. We anticipate that first encountered groundwater will be at similar depths during the drilling of the monitoring wells. Actual depths will be determined in the field, based on the conditions encountered. The wells will be drilled and installed by a licensed California C-57 drilling contractor using hollow stem augers. Geosyntec will provide oversight of the drilling operations and well installations. The first well will be continuously logged to obtain geologic information and to visually identify first-encountered groundwater. Soil samples from the remaining wells will be collected for logging purposes at approximately 5-ft intervals. Soil cuttings will be contained in 55-gallon drums. Soil samples will not be collected for chemical analysis unless unusual soil conditions are noted during drilling.